Effects of Waxy Rice Moisture Content and Rate of CO₂ Injection on Characteristics of Extruded Pellets and Vacuum‐Puffed Yukwa (a Korean Traditional Snack)

Abstract

Extrusion with CO2 injection was developed to simplify the process of producing vacuum‐puffed yukwa (rice snacks). The effects of feed moisture content and CO2 injection on the characteristics of extruded pellets (maximum viscosity and degree of gelatinization) and vacuum‐puffed yukwa (expansion ratio, bulk density, hardness, and color) were investigated. Higher feed moisture increased the size of vacuum‐puffed yukwa and the degree of gelatinization, whereas the maximum viscosity decreased. Maximum viscosity and gelatinization degree of extruded pellets were highly correlated with expansion ratio, bulk density, hardness, and color values of vacuum‐puffed yukwa. Increasing feed moisture content significantly increased expansion ratio but decreased bulk density and hardness. CO2 injection decreased bulk density and hardness of vacuum‐puffed yukwa.

Effects of different blowing agents on physical properties of extruded puffed snacks made from yellow pea and red lentil flours

“…When physical blowing agent injection pressure was increased further (>300 kPa), extrudate hardness increased (Koksel & Masatcioglu, 2018). A decrease in extrudate hardness with CO 2 injection has been reported for sorghum-apple pomace blend extrudates (Lohani & Muthukumarappan, 2017) and extruded pellets made from waxy rice (Shen et al, 2013). The findings of these studies indicate that extrudate hardness is not only affected by physical blowing agent type and injection pressure but also affected by raw material used, potentially explaining the differences in extrudate hardness response as a function of gas type (N 2 vs. CO 2 ) and pulse type (red lentil vs. yellow pea).…”

“…For extrudates made from red lentil flour, the presence of N 2 caused a statistically significant ( p < 0.05) increase in extrudate hardness, while hardness of extrudates made from yellow pea flour was not substantially affected by physical blowing agents. It has been previously reported that injection pressure of the physical blowing agent substantially affects extrudate hardness (Koksel & Masatcioglu, ; Lohani & Muthukumarappan, ; Shen et al, ). For example, at low physical blowing agent injection pressures (100–300 kPa), extrudates made from yellow pea flour were shown to have hardness values similar to those of extrudates produced by conventional extrusion.…”

“…Typically, extrudate density and expansion have an inverse relationship, as blowing agents assist in extrudate radial expansion and cause a reduction in extrudate density (Koksel & Masatcioglu, 2018;Meng, Threinen, Hansen, & Driedger, 2010;Shen et al, 2013). However, expansion is not only restricted to radial direction, since it includes longitudinal expansion as well.…”

“…The most common physical blowing agent in food extrusion is CO 2 in its supercritical or subcritical form. The use of CO 2 during extrusion to enhance texture and structure of foods has been investigated in a variety of products such as sorghum flour, cornmeal, waxy rice, and wheat (Lohani & Muthukumarappan, ; Samard et al, ; Shen, Gil, & Ryu, ; Singkhornart et al, ) but not for pulse products. Moreover, the use of physical blowing agents other than CO 2 is quite rare in food extrusion, especially for higher protein and/or fiber containing raw materials such as pulses, with only one recent study focusing on N 2 gas as a physical blowing agent during extrusion cooking of yellow pea flour (Koksel & Masatcioglu, ).…”

“…The most common physical blowing agent in food extrusion is CO 2 in its supercritical or subcritical form. The use of CO 2 during extrusion to enhance texture and structure of foods has been investigated in a variety of products such as sorghum flour, cornmeal, waxy rice, and wheat (Lohani & Muthukumarappan, 2017;Samard et al, 2017;Shen, Gil, & Ryu, 2013;Singkhornart et al, 2014) but not for pulse products.…”